On Sat, Jan 27, 2024 at 01:08:02PM +0000, Peter Maydell wrote: > On Fri, 26 Jan 2024 at 20:49, Markus Armbruster <arm...@redhat.com> wrote: > > > > Peter Maydell <peter.mayd...@linaro.org> writes: > > > > > Hi; one of the "bitesized tasks" we have listed is to convert > > > watchdog timers which directly call qemu_system_reset_request() on > > > watchdog timeout to call watchdog_perform_action() instead. This > > > means they honour the QMP commands that let the user specifiy > > > the behaviour on watchdog expiry: > > > https://www.qemu.org/docs/master/interop/qemu-qmp-ref.html#qapidoc-141 > > > https://www.qemu.org/docs/master/interop/qemu-qmp-ref.html#qapidoc-129 > > > (choices include reset, power off the system, do nothing, etc). > > > > > > There are only a few remaining watchdogs that don't use the > > > watchdog_perform_action() function. In most cases the change > > > is obvious and easy: just make them do that instead of calling > > > qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET). > > > > > > However, the hw/watchdog/spapr_watchdog.c case is trickier. As > > > far as I can tell from the sources, this is a watchdog set up via > > > a hypercall, and the guest makes a choice of "power off, restart, > > > or dump and restart" for its on-expiry action. > > > > > > What should this watchdog's interaction with the watchdog-set-action > > > QMP command be? If the user says "do X" and the guest says "do Y", > > > which do we do? (With the current code, we always honour what > > > the guest asks for and ignore what the user asks for.) > > > > Gut reaction: when the user says "do X", the guest should not get a say. > > But one of the values of X could be "whatever the guest says".
That would also be my inclination.
> Mmm. Slightly awkwardly, we don't currently distinguish between
> "action is reset because the user never expressed a preference"
> and "action is reset because the user specifically asked for that",
> but I guess in theory we could make that distinction. (Conveniently
> there is no QMP action for "query current watchdog-action state",
> so we don't need to worry about reflecting that distinction in the
> QMP interface if we make it.)
I think that change is necessary in order to accomodate this sort of
watchdog with guest-progammable behaviour (which is part of the PAPR
spec, so we shouldn't just ignore it).
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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